This invention relates to refiner members for refiners for lignocellulose-containing fibrous, preferably vegetable material, which members comprise a carrier and connected thereto at least one ring of segments of a hard material which form the refining surface of said member.
According to a usual design, the refining members are discs, on which one or more rings of segments are attached about the radial lateral surface of the disc-shaped carrier. The refiner comprises at least one pair of discs, which are rotatable relative to and maintained with pressure against each other. In the gap formed between the discs, the material to be refined, for example wood chips, is disintegrated to fibre pulp. The gap is defined by segments, the surfaces of which facing toward each other are formed with elevations in the form of grooves and, respectively, bars or the like, the object of which is to promote the processing of the material in order to expose fibres and, respectively, fibrils. In modern refiners the rotary disc rotates at a high speed and has a great diameter, and the segments, therefore, are subjected to very high centrifugal forces. As an example can be mentioned, that at segments with a weight of some tens of kilos centrifugal forces of the magnitude 50 Mp can arise.
The segments normally are attached on the disc-shaped carrier or holder of the refiner disc by means of bolts, which are screwn into the segments from the rear side thereof. In view of the very high stresses, a plurality of bolts are used for each segment, but the stresses arising in the segments proper yet are so high, that the segments must be designed with a thickness, and thereby with a weight, which by far exceeds what is required for forming the grooves and bars therein. In addition, in order to obtain the highest possible wear resistance, the segments must be manufactured of a very hard material, which from a strength point of view cannot be calculated safely. The segments, thus, have been overdimensioned to a high degree. This additionally increases the stresses in the segments and attachment bolts. Owing to their great thickness, the segments by action of the centrifugal forces also are subjected about their outer periphery to a high torque, which tends to swing the segments out from the carrier.
At another embodiment, the segments are attached on the carrier by means of keyingly interengaging grooves and bars and an overall locking ring, which takes up the centrifugal forces acting on the segments. This implies that each segment behind its processing surface can be designed less thick than required at the use of bolts. Hereby the centrifugal forces and, thus, the stresses are reduced.
Such a design, however, renders exchange of one or more segments difficult. The refiner must be taken out of operation for a reletively long time, because the entire locking ring must be dismantled. This design further requires a very high precision of the outer diameter of the segments, because each segment must be connected to the carrier by the locking ring with no clearance at all.
The present invention solves the aforesaid problems and renders possible a substantially simplified attachment of the disc segments on the carrier by means of separate locking members without jeopardizing the operation reliability. The segments thereby can be exchanged much more rapidly and simply, and at the same time the manufacturing costs of the segments can be reduced.